The applicants and others have reported that mast cells an eosinophils represent potential sources of several different multifunctional cytokines. In published studies, we showed that freshly isolated mouse mast cells represent a significant source of both preformed and immunologically inducible TNF-alpha, that IgE-dependent leukocyte infiltration in the skin of mice in vivo is entirely mast cell-dependent and is significantly dependent on TNF-alpha, and that in vitro-derived mouse mast cells represent a source of a broad panel of cytokines in addition to TNF-alpha. We also showed that human eosinophils represent a potentially significant source of two cytokines: TGF-alpha and TGF-beta1. In addition, we have obtained data indicating that eosinophils can produce IL-1alpha and that both human lung mast cells and the blood eosinophils of eosinophilic donors can produce the pro-inflammatory cytokines TNF-alpha and MIP-1alpha. Among their many activities, TNF-alpha, IL-1alpha and MIP-1alpha can promote leukocyte infiltration, TGF-alpha can induce epithelial proliferation, and TGF-beta1, IL-1alpha, and TNF-alpha can promote fibrosis. Based on these findings, we have formulated the hypothesis that multifunctional cytokines produced by mast cells and eosinophils may importantly influence many aspects of allergic disorders, such as leukocyte infiltration, epithelial proliferation, and tissue fibrosis. However, little is known of the regulation of cytokine production by human mast cells or eosinophils, nor is it clear to what extent human mast cells or eosinophils represent a significant source of cytokines at sites of allergic disorders in vivo. To address these gaps in our knowledge, we wish to pursue the following three aims: 1. Analyze the ability of anti-IgE and other relevant stimuli to induce human mast cells to synthesize and release TNF-alpha and other cytokines in vitro, and determine whether corticosteroids or other pharmacological agents can interfere with the ability of these cells to produce cytokines. 2. Analyze the regulation of eosinophil production of TGF-alpha, TGF-beta, TNF-alpha, IL-1alpha, and other cytokines in vitro, using eosinophils derived from subjects with eosinophilia due to the idiopathic hypereosinophilic syndrome or other causes, or from normal donors, and determine whether eosinophil cytokine production can be suppressed with corticosteroids. 3. Use in situ hybridization (ISH) and immunohistochemistry (IHC): 1) to evaluate the expression of cytokines by mast cells and eosinophils actually participating in the lesions of asthma, allergic rhinitis, atopic dermatitis and other disorders, or in the lesions of experimental late phase reactions elicited in the lung, nose, and skin, 2) to assess the importance of mast cells and eosinophils, as opposed to other cell types, as potential sources of cytokines in these responses, 3) to establish whether mast cell and eosinophil cytokine expression in these settings is associated with such potentially cytokine-dependent findings as leukocyte infiltration or epithelial cell or fibroblast proliferation, and 4) to evaluate whether corticosteroid treatment diminishes mast cell and eosinophil cytokine production at these sites.